Spring cushioning devices



Feb. 6, 1962 J. K. BACI-:E ETAL 3,020,037

SPRING CUSHIONING DEVICES Filed oct. 12, 1959 s' sheets-sheet 1 ATTORNEYS Feb. 6, 1962 J. K. BAcHE ETAL 3,020,037

SPRING CUSHIONING DEVICES Filed OC. 12,A 1959 3 Sheets-Sheet 2 Feb. 6, 1962 J. K. BACI-1E ETAL 3,020,037

SPRING CUSHIONING DEVICES Filed Oct. 12, 1959 3 Sheets-Sheet 5 ATOR/VEVS United States Patent 3,029,037 SPRWG CUSHlGNlNG DEVCES .lohn Kenneth Baci-ie, 144 High St., West Bromwich,

England, and George German, 11 Clerkenwell Crescent, Malvern, England Filed Get. l2, 1959, Ser. No. 845,983 Claims priority, application Great Britain Oct. 15, 1958 6 Claims. (Cl. 267-1) This invention relates to spring cushioning devices whichy are particularly suitable for use in the packaging of delicate materials or apparatus requiring protection from excessive shock forces during transit.

lt is known to package such delicate materials or apparatus, for example electronic apparatus, in packaging containers comprising an inner crate or casing which is lioatingly supported in `an outer crate or casing by means of coiled compression springs or compressible resilient material such as sponge rubber. For a predetermined cushioning efficiency, however, such known cushioning means has suliered from the disadvantage oi requiring a relatively large volume or wasted space to be left between the inner `and outer packaging casings. t is clearly desirable where transport costs depend upon bulk and where storage space is limited that the space between rhe inner yand outer casings should be reduced to a minie mum consistent with adequate protection against likely shock forces, and it is an object of the present invention to provide a compact and eliicient spring cushioning device which enables the cushioning space to be kept to a minimum. y

With the use of known compression springs and compressible resilient material, not only is the deection under load relatively large for a given loading force and given energy absorption, but when fully compressed the cushioning means occupies a relatively large amount of dead space, and both these features contribute to the requirement fora relatively large volume of Wasted packaging space. Accordingly, a more specic object of the present invention is to provide a spring cushioning device in which a given load can bring about a small deflection and greater energy absorption than conventional known coil spring or compressible resilient material devices, and at the same time, will occupy la smaller dead space when fully compressed.

According to the invention, a spring cushioning device for separating and spacing apart two relatively-movable members, such as inner and outer casings of apackaging container, comprises a plurality of lever arms adapted to be interposed between opposed surfaces of said two members and operatively connected or integral with torsion `bars `arranged parallel to one another, each lever arrn extending laterally with respect to the longitudinal torsional axis of its associated torsion bar whereby, in use, upon movement of the said two members towards one another, the lever arms are angularly deflected and apply =a twisting couple to the torsion bars thereby generating au opposing torsional stress, the effective lengths of the lever arms increasing progressively with the extent of deflection. Preferably, the lever arms are formed by the integral end portions of a plurality of substanti ally straight torsion bars aligned -side-by-side, said end portions forming the lever arms being bent up so as to extend in planes transverse to the longitudinal torsional axes or the torsion ibars. The other ends of the torsion bars are suitably restrained `from twisting and torsion bars associated with lever arms inclined in opposite directions may be joined together in pairs so that, in effect, the torsion rods or bars of each pair are formed by the opposite parallel side limbs of a U.

The outer ends of the lever `arms `may support a pressure plate and are preferably `arranged to be slidably ice movable in grooves on the underside of the pressure plate so as to permit of spreading when the plate is depressed under load. In the normal nov-load condition, the ends of the lever arms may rest at one end of the grooves and on cam surfaces which facilitate the initial spreading movement.

By way of example, a convenient embodiment of the invention will now be more particularly described, with reference to the accompanying drawings, in connection with a spring cushioning device suitable for use in the packaging for transport of delicate electronic equipment which is to be packed in an inner crate or casing adapted to be enclosed within a larger outer crate or casing. The spring cushioning device is intended for interposition between said inner and outer crates or casing so as to provide a floating support.

In said accompanying drawings, i

FIGURE 1 is an end elevational view of the cushioning device shown in interposed position between the walls of respective inner and outer casings of a packaging container;

FIGURE 2 is a side elevational view of the device;

FGURE 3 is a top plan view of the device; f

FIGURE 4 is a sectional view along line lV--lV of FlGURE 2;V

FGURE 5 is a. transverse section in line V-V of FlGURE 4;

FIGURE 6 is a transverse section on line Vl-VI of FIGURE 3;

' FIGURE 7 is `a section on line Vll-Vl of FlGURE 2;

FIGURE 8 is a view similar to FIGURE 7, but shows the device under load;

FlGURE 9 is a perspective view of a modiiied form of cushioning device; and

FIGURES l0 to 13 show diagrammatically various yalternative means of effecting a pre-stressing of the device.

The spring cushioning device illustrated in FIGURES 1 to 8 of the drawings comprises an even number of elongated torsion rods or bars 1 which are formed by the parallel side limbs of a plurality of U-shaped lengths of heavy gauge wire and which are aligned in a'sideby side relationship, pairs of the torsion rods or bars 1 corresponding to each- U being arranged symmetrically about a common medial plane.

The Ushaped length are sized so as to nest togethe and the closed inner ends 2 are enclosed within a at sheet-metal housing 3 intended to be secured tothe in-l terior faceof the outer crate or casing 4.

At the other or outer end, the assembly of torsion rods or bars 1 seats upon a short base plate 5 which carries a bridge piece 6 forming a retaining and locating sleeve for maintaining the rods or bars 1 in their correct relative positions. The underside of the base plate 5 forms a pressure surface for bearing upon the interior face of the outer crate or container 4 during use. Also, at this outer end, integral extensions of the torsion bars or rods l are bent up at right angles so as to lie in trans,- verse planes substantially perpendicular to the longitudinal torsional axes of the torsion rods o r bars to form lever arms 7, the lever'arnis of corresponding pairs of the torsion rods or bars 1 being inclined in' opposite directions so as to cross over one another alternately. The free outer ends 8 of successive lever arms 7 are thus directed away from one another and support a pressure plate 16 which is adapted to bear against the outer face oi the inner crate or casing 1,1.

The pressure plate 10 is in the form of a substantially rectangular sheet metalpressing formed on its underside with a plurality of longitudinallyfextending parallel grooves or channels 12 which are arranged on either side f 3 of a plain depressed middle portion 13 of the plate 10 and which receive the free outer ends 8 of said lever arms 7.

'Ihe outer ends of these grooves or channels 12 extend to the respective ends of the plate 10, and the inner ends of the grooves or channels merge into the plain depressed middle portion 13, forming inclined cam surfaces 15 against which the ends 8 of the lever arms 7 normally bear when the device is not under load (see FIG- URE 7).

The underside of the pressure plate is covered by a retaining plate 16 which is secured in place by rivets 17 and which is provided with slots or openings 14 through which the outer end portions 8 of the lever arms are passed. By turning over the tips of the ends 8 of some of the lever arms 7, as shown at 88- (FIGURE 6), so that they are trapped behind the slotted retaining plate 16, separation of 'the pressure plate is prevented and the inner ends of the grooves 12 form stops preventing inward movement of the lever arms beyond the inclined cam surfaces 15.

Preferably, in the initial no load position with the lever arms 7 set as described and shown in FIGURES l, 2 and 7, the torsion bars or rods 1 are arranged to be under an initial torsional stress so that a force is exerted on the lever arms tending to move their outer ends 8 inwards against the cam surfaces of the pressure plate 10. When a load is applied to the pressure plate 10 suicient to overcome the restoring force exerted on the lever arms by this pre-stressing, the pressure plate starts to move downwards and the ends of the oppositely-in clined lever arms are moved further apart from each other, being caused to ride down the cam surfaces 15 and slide along the grooves or channels 12 (see FIG- URE 8). This movement of the lever arms 7 is, of course, resisted by the increasing torsional stress imposed upon the torsion rods or bars 1, but at the same time, the effective length of the lever arms is increased since they deflect angularly as the outer ends 8 move further apart, thereby resulting in an increased twisting couple being exerted upon the rtorsion rods or bars 1 for a given load. These two effects tend to counteract one another and, it may be arranged so that very little deflection of the pressure plate 10 occurs until a predetermined load is reached, but thereafter a small further increase in load is sufficient to cause relatively large defiections of the pressure plate with a corresponding large absorption of energy. This is a very desirable characteristic of a spring cushioning device of this character since it enables the predetermined load at which the device beginsto respond to be arranged to be safely below the maximum permissible force which may be applied to the goods being packaged without harm, and an applied shock loading force will not increase much above this predetermined load and will not exceed the maximum safe value unless very severe shocks are encountered. In contrast with a simple coil spring which has a substantially linear load/deflection characteristic, a spring cushioning device as described will be capable of absorbing a much greater amount of energy before a predetermined maximum load is exceeded, and this difference in behaviour is even more marked in contrast with the characteristics of a compressible resilient material such Y as foam rubber.

A'further very advantageous feature of the spring cushion device herein described is that when the pressure plate 10 is fully depressed, the lever arms 7 spread to their maximum extent and the pressure plate may approach very close to the torsion rods or bars 1 and base plate 5 which, in use, lies against the inner face of the outer packaging container, so that there is very little dea d space such as must be allowed for with a coil spring. Also, in contrast with a compressible resilient cushioning material such as ,foam rubber, the present cushioning device has the advantage that it is not liable to deteriorate readily due to adverse climatic conditions.

The exact form of the load/ deflection characteristics is influenced by the frictional resistance to sliding of the ends of the lever arms 7 on the underside of the pressure plate 10, and this frictional effect is most marked in the initial position when the relative inclinations of the lever arms are a minimum. In this respect it will be understood that the inclined cam surfaces 15 act in facilitating and controlling the initial spreading of the lever arms 7 under load and are useful in enabling the desired characteristics to be obtained with a compact assembly, but their presence, although desirable, is not essential for the carrying out of the invention.

As shown in FIGURE 2, the torsion rods or bars 1 may be formed with a small curvature along the direction of their length so that the base plate 5 can be initially slightly spaced from the surface of the outer casing 4. rIlle torsion rods or bars can be readily flexed along their length so that a light load will be sucient to bring the device into its fully operative position, but this additional resiliency is useful for accommodating the device to the exact dimensions of the space between the inner and outer crates or casings 11 and 114 of the packaging container.

In use, it will be understood that a plurality of these devices will normally be employed, at least one being positioned on every side of the inner casing 11 so that the latter is oatingly supported. If desired, the arrangement of use hereinbefore described may be reversed, the pressure plate 10 being arranged to bear on the outer casing 4, and the torsion rods or bars 1 being carried by the inner casing 11.

It is not essential for a pressure plate to form a component part of the cushioning device as does the plate in the above-described embodiment. In the modification illustrated in FIGURE 9 the general arrangement of a plurality of parallel torsion bars 1a carrying integral oppositely-inclined lever arms 7al is the same as in the first embodiment, but the outer free ends 8b of the lever arms 7a are adapted to bear directly on the surface of the inner (or outer) casing of the packaging container. Thus, it will be seen from FIGURE 9 that these outer ends 8b are curled over to provide a smooth bearing surface, and preferably in use, the co-operating surface of the packaging casing will be covered with a metal plate to minimize Wear as these ends 8h of the lever arms 7a slide in contact therewith when under load.

Means for imparting a predetermined degree of prestressing to the device of FIGURE 9 comprises two lengths of flexible wire cable 20 which are securely anchored to a base plate 21 and passed through sleeves 22 embraced by the curled over end 8b of the lever arms 7a. One end of each length of cable 20 is anchored by lugs 23, and the other end may be similarly secured or, as shown, it may be adjustably secured by a clamping screw 24 and sleeve 25 such that the degree of tension in the cable can be readily set to the required value. The torsion bars 1a are integrally formed as Ushaped pairs, as in the first embodiment, and their joined inner ends are nested and retained in place in a sheet metal housing 3a.

It is not essential that the inner ends of the torsion rods or bars be joined in pairs in a U-form as described but if desired, each torsion rod or bar could be separate with their inner ends anchored and restrained individually against twisting. The U-forrn described, however, results in the important advantage that torque reaction on the housing or associated bearing surface is avoided.

With oppositely inclined lever arms arranged to cross over one another as in the herein-described embodiments other means of effecting the pre-stressing may readily be devised. For example, as indicated in FIGURE l0 a single cable 30 under tension and anchored to the base plate 31 may be passed through, and seated in, the apex of the angle formed between the two series of oppositelyinclined lever arms 7b. Alternatively, as indicated in FIGURE 11, a locking bar 32 may be seated in the apex of this angle and be coupled by flexible cable 33 at each end to the base plate 3i. Another means of effecting the pre-stressing is to shape the oppositely-inclined lever arms 7b, such as by cranked portions 3S in the middle, as shown in FIGURE 12, so that they interlock when they approach each other to within a predetermined distance apart. Or, a separate abutment member 36 may be secured to the one series of lever arms '7b such that it co-operates with the series of oppositely-inclined arms, as shown in FIG- URE 13. All these various means have the same object, that is to prevent the lever arms from all returning independently to their unstressed positions.

In a further form, instead of the lever arms being inclined in opposite directions towards one another so that those associated with corresponding pairs of torsion rods or bars cross over one another, they may, if desired, be inclined away from one another so as not to cross over. Also, any desired number of torsion rods and lever arms may be used.

We claim:

l. A spring cushioning device comprising a plurality of parallel torsion bars, means for resisting twisting of one end of each torsion bar, a plurality of lever arms joined to respective torsion bars and extending laterally with respect to the longitudinal torsional axes of the torsion bars, pressure surfaces associated with the respective ends of said lever arms, the respective lever arms of pairs of said torsion bars being inclined in opposite directions with respect to the pressure surfaces whereby movement under load towards one another of said pressure surfaces angularly deflects said lever arms and applies a twisting couple to the torsion bars, the effective lengths of the lever arms increasing progressively with the extent of deflection and the oppositely-inclined lever arms defiecting in opposite angular directions, and pre-stressing means comprising a common stop member co-operable with said oppositelyinclined lever arms to limit the minimum deliection of the latter and produce a predetermined minimum torsional stress.

2. A spring cushioning device according to claim 1 in which said oppositely-inclined lever arms cross over each other in the normal initial condition of the device.

3. A spring cushioning device comprising a plurality of parallel torsion bars, means for resisting twisting of one end of each torsion bar, said means including integral connecting parts joining said ends of pairs of the torsion bars, a plurality of lever arms integral with the other ends of the respective torsion bars and extending laterally with respect to the longitudinal axes of the torsion bars, pressure surfaces associated with the respective ends of said lever arms, the respective lever arms of pairs of said torsion bars being inclined in opposite directions with respect to the pressure surfaces whereby movement under load towards one another of said pressure surfaces angularly deflects said lever arms and applies a twisting couple to the torsion bars, the elective lengths of the lever arms increasing progressively with the extent of deflection and the oppositely-inclined lever arms deecting in opposite angular directions, and pre-stressing means comprising a stop arrangement to limit the minimum dellection of the lever arms and to produce a predetermined minimum torsional stress.

soL

4. A spring cushioning device comprising a plurality of U-shaped lengths of spring steel rod nested together, parallel side limbs of which constituting torsion bars, integral extension parts constituting lever arms at the outer ends of said parallel side limbs directed in planes substantially at right angles to the axes of the side limbs, and two spaced pressure plates associated respectively with the respective inner and outer ends of the lever arms, the two lever arms associated with the pair of torsion bars constituted by each U-shaped length of rod being inclined in opposite directions with respect to the pressure surfaces whereby movement under load towards one another of said pressure surfaces angularly deiiects said lever arms and applies a twisting couple to the torsion bars, the effective lengths of the lever arms increasing progressively with the extent of deflection and the oppositely-inclined lever arms deilecting in opposite angular directions, and pre-stressing means comprising a common stop member co-operable with said oppositely-inclined lever arms to limit the minimum deflection of the latter and produce a predetermined minimum torsional stress.

5. A spring cushioning device comprising a plurality of parallel torsion bars, means for resisting twisting of one end of each torsion bar, a plurality of lever arms joined to respective torsion bars and extending laterally with respect to the longitudinal torsional axis of the torsion bars, a pressure plate associated with the respective inner ends of said lever arms adjacent the torsion bars, a second pressure plate carried by the respective outer ends of said lever arms, and means on the underside of said second pressure plate for guiding and retaining the outer ends of the lever arms, the respective lever arms of pairs of said torsion bars being inclined in opposite directions with respect to the pressure plates whereby movement under load of the pressure plates towards one another angularly deilects said lever arms and applies a twisting couple to the torsion bars, the eitective lengths of the lever arms increasing progressively with the extent of deilection and the oppositely-inclined lever arms deecting in opposite angular directions and their outer ends moving away from one another in sliding contact with said second pressure plate.

normal no-load condition of the device whereby the i initial spreading movement of the lever arms under load is facilitated and controlled.

References Cited in the file of this patent UNITED STATES PATENTS Re. `6,205 Saladee Ian. 5, 1875 113,166 Hershey Mar. 2S, 1871 114,136 Hershey Apr. 25, 1871 1,559,043 Goldberg Oct. 27, 1925 2,703,233 Johnson Mar. 1, 1955 2,928,536 Weaver et al. Mar. `15, 1960 FOREIGN PATENTS 873,625 Germany Apr. 16, 1953 

